Introduction to Quality and Statistical Process Control CD-ROM Chapter 16 Introduction to Quality and Statistical Process Control

Chapter 16 - Chapter Outcomes After studying the material in this chapter, you should be able to: Use the seven basic tools of quality. Construct and interpret x-bar and R charts. Construct and interpret p-charts. Construct and interpret c-charts.

Quality Management Total Quality Management refers to a journey to excellence in which everyone in the organization is focused on continuous process improvement directed toward increased customer satisfaction.

Deming’s 14 Points 1. Create a constancy of purpose toward the improvement of products and services in order to become competitive, stay in business, and provide jobs. 2. Adopt the new philosophy. Management must learn that it is a new economic age and awaken to the challenge, learn their responsibilities, and take on leadership for change. 3. Stop depending on inspection to achieve quality. Build in quality from the start. 4. Stop awarding contracts on the basis of low bids. 5. Improve continuously and forever the system of production and service to improve quality and productivity, and thus constantly reduce costs.

Deming’s 14 Points 6. Institute training on the job. 7. Institute leadership. The purpose of leadership should be to help people and technology work better. 8. Drive out fear so that everyone may work effectively. 9. Break down barriers between departments so that people can work as a team.. 10. Eliminate slogans, exhortations, and targets for the workforce. They create adversarial relationships. 11. Eliminate quotas and management by objectives. Substitute leadership. 12. Remove barriers that rob employees of their pride of workmanship.

Deming’s 14 Points (continued) 13. Institute a vigorous program of education and self-improvement. 14. Make the transformation everyone’s job and put everyone to work on it.

Quality Management The Pareto Principle states that 80% of the trouble comes from 20% of the causes.

Juran’s 10 Steps to Quality Improvement 1. Build awareness of both the need for improvement and the opportunity for improvement. 2. Set goals for improvement. 3. Organize to meet the goals that have been set. 4. Provide training. 5. Implement projects aimed at solving problems. 6. Report progress. 7. Give recognition. 8. Communicate the results. 9. Keep score. 10. Maintain momentum by building improvement into the company’s regular systems.

The Deming Cycle (Figure 16-1) Plan The Deming Cycle Act Do Study

The Basic 7 Tools Process Flowcharts Brainstorming Fishbone Diagram Histogram Trend Charts Scatter Plots Statistical Process Control Charts

Problem Solving Process (Figure 16-2) Issue Surfaces The Tools of Quality Organize Team Define the Problem Identify and Analyze Causes Identify Solutions and Options Test Solutions Track and Evaluate

Outline of a Fishbone Diagram (See Figure 16-4)

Statistical Process Control Charts Inherent variation refers to the variation in the output of a process that exists naturally. This variation can be reduced but not eliminated.

Statistical Process Control Charts Three concepts to remember about variation are: •Variation is natural; it is inherent in the world around us. •No two products or service experiences are exactly the same. •With a fine enough gauge, all things can be seen to differ.

Statistical Process Control Charts The six most common sources of variation are: • People • Machines • Materials • Methods • Measurement • Environment

Statistical Process Control Charts Common cause variation is the variation in the output of a process that is naturally occurring and expected and that may be the result of natural variation in materials, tools, machines, operators, and the environment.

Statistical Process Control Charts Special cause variation is the variation in the output of a process that is abnormal or unexpected and which has an assignable cause. Variation in the output that is beyond that which is considered inherent to the process.

Statistical Process Control Charts VARIATION COMPONENTS Total Process Variation = Common Cause + Special Cause Variation Variation

Statistical Process Control Charts A subgroup is a sample of items selected from a process.

Steps Involved in Creating x-bar and R-Charts • Calculate subgroup means and ranges. • Compute the average of the subgroup means and the average range value. • Prepare graphs of the subgroup means and ranges as a line chart. • Compute the upper and lower control limits for the x-bar chart. • Compute the upper and lower control limits for the R-chart. • Finish constructing the control chart by locating the control limits on the x-bar and R-charts.

Statistical Process Control Charts AVERAGE OF SUBGROUP MEANS where: = ith subgroup average k = Number of subgroups

Statistical Process Control Charts AVERAGE OF SUBGROUP MEANS where: Ri = ith subgroup range k = Number of subgroups

Statistical Process Control Charts UPPER CONTROL LIMIT where: A2 = Shewhart factor for subgroup size = n

Statistical Process Control Charts LOWER CONTROL LIMIT where: A2 = Shewhart factor for subgroup size = n

Statistical Process Control Charts UPPER CONTROL LIMIT where: D4 is taken from the Shewhart table for subgroup size = n

Statistical Process Control Charts LOWER CONTROL LIMIT where: D3 is taken from the Shewhart table for subgroup size = n

Statistical Process Control Charts An attribute refers to a quality characteristic that is either present or not in an item.

Statistical Process Control Charts MEAN SUBGROUP PROPORTION For equal size samples: where: pi = Sample proportion for subgroup i k = Number of subgroups of size n

Statistical Process Control Charts MEAN SUBGROUP PROPORTION For unequal sample sizes: where: ni = The number of items in sample i = Number of items sampled in k samples

Statistical Process Control Charts ESTIMATE OF STANDARD ERROR FOR SUBGROUP PROPORTIONS For equal size samples: where: = Mean subgroup proportion n = Common sample size

Statistical Process Control Charts ESTIMATE OF STANDARD ERROR FOR SUBGROUP PROPORTIONS For unequal samples sizes: Option 1. Compute sp using largest sample size and sp using the smallest sample size. Option 2. Compute a unique value of sp for each different sample size.

Statistical Process Control Charts CONTROL LIMITS FOR p-CHART where: = Mean subgroup proportion sp = Estimated standard error of p

Statistical Process Control Charts MEAN FOR c-CHART where: xi = Number of successes per sampling unit k = Number of sampling units

Statistical Process Control Charts STANDARD DEVIATION FOR c-CHART

Statistical Process Control Charts c-CHART CONTROL LIMITS

Key Terms • Attribute • C-Chart • Centerline • Common Cause Variation • Control Limits • Inherent Variation • p-Chart • Pareto Principle • R-chart • Shewhart Table • Special Cause Variation • Statistical Process Control Chart • Subgroup

Key Terms (continued) • Total Quality Management • x-bar Chart